Telephone devices (e.g., mobile telephones, smart phones, landline telephones, etc.) have been configured to display caller identity (“call ID”) information for incoming calls. For example, if Alice calls Bob from a telephone device associated with the telephone number (123) 456-7890, Bob's telephone device can display Alice's telephone number ((123) 456-7890) and/or her name in association with the incoming telephone call.
A variety of techniques can be used to transmit caller identity information to a call recipient, such as frequency shift keying (FSK). FSK permits for bits of data to be transmitted to a telephone device as part of a telephone call. For example, a first tone (e.g., 1,200 Hertz) can represent a one, and a second tone (e.g., 2,200 Hertz) can represent a zero. Call ID information can be transmitted to a telephone device receiving a telephone call through a series of tones that, when interpreted using a caller identity transmission protocol (e.g., ASCII encoding, particular data packet size and fields, etc.), indicate a caller's identity (e.g., telephone number, name, etc.).